Taking advantages of superiorities in sanitary properties, workability, chemical resistance, weather resistance, electric characteristics and mechanical strength etc., thermoplastic resin has been commonly used for various fields such as buildings, interior decorations and automobile parts as well as fields of electric products for industries and homes, and application use of the thermoplastic resin has been enlarged. Because of such enlargement of application use, flame retardancy began to be requested for thermoplastic resin, and performance requirements are getting more rigorous year after year. Recently in particular, flame retardants such as halogen-containing compound alone or a combination of it with an antimony compound such as antimony oxide have been added to the thermoplastic resin to produce flame-retardant thermoplastic resin composition, which has been a mainstream of the conventional flame-retarding technique. However, it has a defect that the halogenated gases are generated when the flame-retardant resin compositions are burned or molded. Therefore, flame-retardant resin composition, which does not generate the halogenated gases when burned or molded is required.
In order to meet these needs, a method was proposed wherein a specific metallic hydrate, which can inhibit resin burning by performing an endothermal reaction to cause decomposition and dehydration reactions at the burning temperature of resin, was combined as an inorganic flame retardant. However, the metallic hydrate used for this method has only extremely slight flame retardancy. Therefore, it is necessary to combine a large amount of this metallic hydrate in order to produce a flame-retardant effect. In the result, problems occur wherein molding workability of flame-retardant resin composition obtained becomes poor and mechanical strength of molded material obtained decreases.
Recently, in order to meet the above needs, methods using specific phosphorus compounds are proposed which are fire prevention materials by combining ethylenediamine phosphate with salts of melamine and/or cyanuric acid derivatives (such as phosphoric acid melamine) (Patent document 1) and flame-retardant thermoplastic resin compositions which contain phosphates such as phosphoric acid alkyldiamine as a flame retardant (Patent document 2).
However, the above ethylenediamine phosphate and phosphoric acid alkyldiamine have high water-solubility. Therefore, fire prevention materials or flame-retardant thermoplastic resin compositions containing them have poor water resistance and can not be used for the use wherein a contact with water is unavoidable, which was a disadvantage.
Furthermore, an intumescent flame retardant is disclosed which exhibits flame retardancy by forming a surface intumescent layer that can inhibit diffusion of decomposition products produced and heat transmission when burned (Patent document 3). However, although this flame retardant has excellent flame retardancy, it has a disadvantage where it is insufficient in water resistance.
A system wherein an ammonium polyphosphate compound and phosphoric acid amine salt are used together to provide a thermosetting resin on the surface of the ammonium polyphosphate compound is disclosed and polycarbodiimide is described as an example of the above thermosetting resin (Patent document 4). However, in this case, water resistance is insufficient and in addition there is no mention that an improvement in the workability of thermoplastic resin is obtained.
Prior Art Document
Patent Document
Patent document 1: Japanese Unexamined Patent Publication Tokkaisho 59-47285
Patent document 2: Japanese Unexamined Patent Publication Tokuhyo-hey 5-508187
Patent document 3: Japanese Unexamined Patent Publication Tokkai 2003-26935
Patent document 4: Japanese Unexamined Patent Publication Tokkai-hei 9-235407